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1 October 2005 Role of FOXO1A in the Regulation of Insulin-Like Growth Factor-Binding Protein-1 in Human Endometrial Cells: Interaction with Progesterone Receptor
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Abstract

Insulin-like growth factor-binding protein-1 (IGFBP1) is a major secretory product of the decidualized endometrium. In the present study, we investigated the role of two transcription factors, progesterone receptor (PGR) and a member of the forkhead box class O family of transcription factors (FOXO1A), in the regulation of the IGFBP1 gene in endometrial cells. Human endometrial fibroblasts (HuF) expressed FOXO1A, progesterone receptor A (PGRA), and progesterone receptor B (PGRB) proteins, whereas the endometrial adenocarcinoma cell line, HEC-1B cells, expressed only FOXO1A and no detectable PGR proteins. When FOXO1A expression was silenced using small interference RNA, IGFBP1 expression decreased in both HuF and HEC-1B cells. Using the chromatin immunoprecipitation technique, we demonstrated that liganded PGR was recruited to the IGFBP1 promoter region (−358 to −49). In addition, immunoprecipitation of HuF nuclear proteins with a PGR antibody followed by immunoblotting with anti-FOXO1A revealed that these two proteins interact in these cells. Reporter studies demonstrated that whereas liganded PGRA or PGRB increased a progesterone response element-linked reporter construct, pPRE/ GRE.E1b.Luc, coexpression of FOXO1A inhibited the PGRB response in HuF and synergistically increased PGRA and PGRB response in HEC-1B cells. Furthermore, in HEC-1B cells, FOXO1A increased IGFBP1 promoter activity, and coexpression of PGRA or PGRB further increased the promoter activity in a cooperative manner. In HuF, the response to FOXO1A and PGR was not additive; in fact, it was lower than the sum of the individual responses. Thus, FOXO1A and PGR associate with one another, and each influences the transactivating potential of the other. The cell type-dependent responses strongly implicate the involvement of other cofactors.

J. J. Kim, O. L. Buzzio, S. Li, and Z. Lu "Role of FOXO1A in the Regulation of Insulin-Like Growth Factor-Binding Protein-1 in Human Endometrial Cells: Interaction with Progesterone Receptor," Biology of Reproduction 73(4), 833-839, (1 October 2005). https://doi.org/10.1095/biolreprod.105.043182
Received: 26 April 2005; Accepted: 1 June 2005; Published: 1 October 2005
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